从EST到UTC的Java日期转换

Question

我在一个应用程序API (DFC)下工作，它给了我一个类似日期的对象(IDfTime)。API自动将日期转换为当地时区(EST)。我需要转换为UTC发送到oracle数据库。出于某种原因，我的代码增加了一个月。我不明白。有人能解释一下这个吗？

修改日期是由应用 API html" target="_blank">返回的类似日期的对象。我已将其转换为字符串，它看起来像预期的那样（对我来说是 EST）。因此，使用日历和简单日期格式将其转换为特定格式的字符串，我可以在SQL更新语句中使用UTC字符串将其发送到数据库。

注意：我正在将调试语句写入由应用程序而不是标准输出生成的批处理作业日志文件。是的，有更好的方法，但这应该是一个快速小部件。

//adjust modify date for UTC to send to database
String dfcDatePattern = "mm/dd/yyyy hh:mi:ss";
String javaDatePattern = "MM/dd/yyyy HH:mm:ss";
String oracleDatePattern = "MM/DD/YYYY HH24:MI:SS";

String strModifyDate = modifyDate.asString(dfcDatePattern);
if (m_debugMode) m_File.writeBytes("DFC Modify Date String: " + strModifyDate + NEWLINE);

TimeZone localTimeZone = TimeZone.getDefault();
TimeZone utcTimeZone = TimeZone.getTimeZone("UTC");
GregorianCalendar cal = new GregorianCalendar();
cal.setTimeZone(localTimeZone);
if (m_debugMode) m_File.writeBytes("DFC Year: " + modifyDate.getYear() + NEWLINE);
if (m_debugMode) m_File.writeBytes("DFC Month: " + modifyDate.getMonth() + NEWLINE);
if (m_debugMode) m_File.writeBytes("DFC Day: " + modifyDate.getDay() + NEWLINE);
if (m_debugMode) m_File.writeBytes("DFC Hour: " + modifyDate.getHour() + NEWLINE);
if (m_debugMode) m_File.writeBytes("DFC Minutes: " + modifyDate.getMinutes() + NEWLINE);
if (m_debugMode) m_File.writeBytes("DFC Seconds: " + modifyDate.getSeconds() + NEWLINE);
cal.set(modifyDate.getYear(), modifyDate.getMonth(), modifyDate.getDay(), modifyDate.getHour(), modifyDate.getMinutes(), modifyDate.getSeconds());
if (m_debugMode) m_File.writeBytes("Converted Modify Date: " + cal.toString() + NEWLINE);
SimpleDateFormat sdf = new SimpleDateFormat(javaDatePattern);
if (m_debugMode) m_File.writeBytes("Modify Date in Local Time Zone: " + sdf.format(cal.getTime()) + NEWLINE);
sdf.setTimeZone(utcTimeZone);
if (m_debugMode) m_File.writeBytes("Modify Date in UTC Time Zone: " + sdf.format(cal.getTime()) + NEWLINE);

updateQueryString = "execute exec_sql with query = 'update dm_sysobject_s set r_modify_date = TO_DATE(''" + sdf.format(cal.getTime())  + "'',''" + oracleDatePattern + "'') where r_object_id = ''" + objectIdString + "'' '";

输出：

DFC Modify Date String: 03/30/2016 11:44:30 [yep, looks good]
DFC Year: 2016
DFC Month: 3   [month looks good here]
DFC Day: 30
DFC Hour: 11   [EST hour]
DFC Minutes: 44
DFC Seconds: 30

[是的，每个部分看起来都很好]

Converted Modify Date: java.util.GregorianCalendar[time=?,areFieldsSet=false,areAllFieldsSet=false,lenient=true,zone=sun.util.calendar.ZoneInfo[id="America/New_York",offset=-18000000,dstSavings=3600000,useDaylight=true,transitions=235,lastRule=java.util.SimpleTimeZone[id=America/New_York,offset=-18000000,dstSavings=3600000,useDaylight=true,startYear=0,startMode=3,startMonth=2,startDay=8,startDayOfWeek=1,startTime=7200000,startTimeMode=0,endMode=3,endMonth=10,endDay=1,endDayOfWeek=1,endTime=7200000,endTimeMode=0]],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2016,MONTH=3,WEEK_OF_YEAR=14,WEEK_OF_MONTH=5,DAY_OF_MONTH=30,DAY_OF_YEAR=90,DAY_OF_WEEK=4,DAY_OF_WEEK_IN_MONTH=5,AM_PM=1,HOUR=3,HOUR_OF_DAY=11,MINUTE=44,SECOND=30,MILLISECOND=399,ZONE_OFFSET=-18000000,DST_OFFSET=3600000]

[扔掉这个，看看我是否能弄清楚发生了什么。我认为这一切看起来都很好]

Modify Date in Local Time Zone: 04/30/2016 11:44:30

【不好！时间是正确的，但它增加了一个月！？UTC时差只有4小时！]

Modify Date in UTC Time Zone: 04/30/2016 15:44:30

[不好！时间按预期正确调整，但仍增加了一个月]

exec_sql to update r_modify_date: execute exec_sql with query = 'update dm_sysobject_s set r_modify_date = TO_DATE(''04/30/2016 15:44:30'',''MM/DD/YYYY HH24:MI:SS'') where r_object_id = ''09ae12f980002934'' '

[这就是我想要的SQL的样子；同一天，但时间根据UTC偏移进行了调整。但是月份Rest了。SQL语法很好（由于API语法看起来很奇怪）；它更新了数据库中的记录；只是月份不对。]

我想我可以通过添加四个小时来暴力破解硬编码偏移量，但我认为以上是“正确”的方式。为什么不起作用？

Answer 1

在java.util中。公历，月为零。要表示三月，你应该通过2而不是3。

java.util.GregorianCalendar[time=?,areFieldsSet=false,areAllFieldsSet=false,lenient=true,zone=sun.util.calendar.ZoneInfo[id="America/New_York",offset=-18000000,dstSavings=3600000,useDaylight=true,transitions=235,lastRule=java.util.SimpleTimeZone[id=America/New_York,offset=-18000000,dstSavings=3600000,useDaylight=true,startYear=0,startMode=3,startMonth=2,startDay=8,startDayOfWeek=1,startTime=7200000,startTimeMode=0,endMode=3,endMonth=10,endDay=1,endDayOfWeek=1,endTime=7200000,endTimeMode=0]],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2016,MONTH=2,WEEK_OF_YEAR=14,WEEK_OF_MONTH=5,DAY_OF_MONTH=30,DAY_OF_YEAR=90,DAY_OF_WEEK=4,DAY_OF_WEEK_IN_MONTH=5,AM_PM=1,HOUR=3,HOUR_OF_DAY=11,MINUTE=44,SECOND=30,MILLISECOND=399,ZONE_OFFSET=-18000000,DST_OFFSET=3600000]